Organic electroluminescence device and photoelectron device using said electroluminescence device

ABSTRACT

An organic electroluminescence device having a substrate, an electrode formed on the substrate, a light emitting layer formed on the electrode, the light emitting layer enabling injection of positive and negative electrical charges therein and an opposing electrode formed with respect to the light emitting layer so that the light emitting layer is arranged between the transparent electrode and the opposing electrode. The light emitting layer contains a light emitting substance for emitting light anisotropically, the light emitting substance having transition dipole moments attributable to a molecular skeleton thereof, and the transition dipole moments being oriented within an angular range from 0 degree to 70 degrees with respect to a direction normal to a side surface of the light emitting layer.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 09/791,835, filedFeb. 26, 2001, the subject matter of which is incorporated by referenceherein.

BACKGROUND OF THE INVENTION

The present invention relates to a new organic electroluminescencedevice; a thin-film, light-weight and high definition organicelectroluminescence device; new photoelectron devices using saiddevices, such as a thin-film flat panel display, small sized portableprojection display, cellular phone display device, portable PC display,real-time electronic bulletin board, light emitting diode, laser,two-dimensional optical pattern generating device, optical computer,optical cross connector and optical router; as well as to the systemsand services using them.

there has been a growing demand for a light-weight, high definition andless costly small-sized flat panel display for use in the various typesof cellular phones, mobile terminals, mobile computers and carnavigation systems being developed. For household and office use, aspace saving desktop display, a flat panel display and wall-mounted TVsets are taking the place of conventional CRT tube displays. Especially,digital signal transmission on the order of hundreds to severalgigabits/sec. has been put into commercial use in both wired andwireless methods, as a result of the increased use of the high-speedInternet and the progress of digital broadcasting. Time is shifting intoan age where general users will exchange a huge amount of information ona real-time basis. Under these circumstances, flat panel displays arerequired to provide a higher speed display to permit digital processing,in addition to being still more light-weight, and having a higherdefinition, a higher luminance and a lower price.

The Liquid Crystal Display (LCD), Plasma Display (PD) and Field EmissionDisplay (FED) are currently under study to meet these requirements. Inaddition to these flat panel displays, new types of flat panel display,referred to as Organic Electroluminescence Devices (OELD) or OrganicLight Emitted Diodes (OLED), have begun to draw attention in recentyears.

The organic electroluminescence device provides a method of causingfluorescent or phosphorescent organic molecules to emit light byallowing an electric current to flow to the organic compound sandwichedbetween a cathode and an anode, thereby displaying information.According to the References (“Major Issues of Organic LED Elements to beSolved and Practical Statistics” edited by the Organic ElectronicsMaterial Research Organization, Bunshin Publishing Co., mid-1999,P.1-11, and “Preface to Current Situation and Issues of Materials andDevices” by Yoshiharu SATO), organic electroluminescence devices havelong been studied mainly with respect to semiconducting crystals, suchasanthracene and perylene.

In 1987, Tang et. al. proposed a two-layered organic electroluminescencedevice laminated with a light emitting organic compound thin film and ahole transporting organic compound thin film (C. W. Tang and S. A. VanSlyke, Appl. Phys. Lett. 51, 913 in 1987). The starting point is that adramatic improvement of light emitting characteristics is enabled (lightemitting efficiency: 1.51 m/W, drive voltage; 10V and luminance: 1000cd/m²). Since then, a pigment doping technique and high molecular OLED,low working function electrode, mask vacuum evaporation system, etc.have been studied.

In 1997, an organic electroluminescence device based on an electricalcharge injection method, called a simple matrix system was partly putinto commercial use. Further, a new organic electroluminescence devicebased on the electrical charge injection method, called an active matrixsystem is currently under study for development. Such an organicelectroluminescence device is operated according to the followingprinciple: A fluorescent or phosphorescent organic light emittingmaterial is made into a thin film between a pair of electrodes, andelectrons and holes are injected from positive and negative electrodes.In the organic light emitting material, the injected electron becomes anorganic one-electron molecule (simply called an electron) entering theLowest Unoccupied Molecular Orbital (LUMO) of a light emitting molecule.The injected hole becomes an organic one-hole molecule (simply calledhole) entering the Highest Occupied Molecular Orbital (HOMO) of thelight emitting molecule. In the organic material, they move toward theopposite electrode. In the middle of the movement, when an electronmeets a hole, a singlet or triplet state of excitation of the lightemitting molecule is formed. As it deactivates while radiating light,light is released.

Generally, many of the organic light emitting materials are those havinga high quantum efficiency with respect to photoexcitation, as in thecase of various laser pigments. If these materials are made to emitlight by electrical charge injection, the electron and hole have a lowerelectrical charge transport performance since many organic compounds areinsulators. A high voltage on the order of hundreds of volts wasrequired in the initial organic electroluminescence device. However,using excellent electrical charge transporting performances of theorganic electrophotographic photoconductor used as a photoconductor of acopying machine, a thin film is divided into two types according tofunction. One is the film used to transport an electrical charge (hole),and the other is the film used to emit light. This separation offunctions of the thin films has improved the light emittingcharacteristics in the above-mentioned Tang's two-layered organicelectroluminescence device.

Recently, a 3-layered organic electroluminescence device has beenreported wherein the electron transport performance of anotherelectrical charge is assigned to a third organic thin film. In addition,separated function type and multi-layered film type organicelectroluminescence devices have been proposed, wherein thin filmsassigned to perform various functions are added; for example, anelectrical charge injection layer is provided to improve thecharacteristics of injecting the hole and electron into the organicmaterial and a hole stop layer to improve the probability ofre-combination between the two. However, the basis for light emitting islight radiation in the process of deactivation in the state ofexcitation from the organic light emitting molecule contained in theorganic light emitting layer. This basis remains unchanged.

According to the References (“Major Issues of Organic LED Elements to beSolved and Practical Statistics” edited by the Organic ElectronicsMaterial Research Organization, Bunshin Publishing Co., mid-1999,P.25-38, and Yuuji HAMADA, “Chapter 2. Current situation and issues ofLight Emitting Material”), a great number of the fluorescent orphosphorescent organic light emitting materials are known to have beendeveloped for a variety of purposes, such as ink, dye and scintillatormaterials. The organic electroluminescence devices are made of theseorganic light emitting materials. They can be broadly classified interms of molecular weight into low molecular and high molecular types.

The low molecular type is formed into thin films according to a dryprocess, such as a vacuum evaporation method, while the high moleculartype is formed into thin films according to the cast method. Failure inthe formation of organic thin films is said to be one of the reasons whya highly efficient device could not be obtained as an organicelectroluminescence device in earlier days before Tang. Conditionsrequired especially for the low molecule type are as follows: (1)Production of a thin film (100 nm level) in the vacuum evaporationsystem, (2) maintainability of a uniform thin film structure afterformation of the film (without segregation crystal), (3) fluorescentlight quantum yield in the solid status, (4) appropriate carriertransport performance, (5) heat resistance, (6) easy refining, and (7)electrochemical stability, etc. Further, this type can be classifiedinto two types according to the light emitting process, that is, thelight emitting material where light is emitted by direct re-combinationbetween electron and hole, and fluorescent material (or dopant material)where light is emitted by photoexcitation caused by the light emittingmaterial. In addition, when viewed from the differences in chemicalstructure, the following materials are known; metallic complex typelight emitting material (8-quinolinol, benzooxazol, azomethine, flavone,etc. as ligand, and Al, Be, Zn, Ga, Eu, Pt, etc. as central metal) andfluorescent pigment based light emitting material (oxadiazole,pyrazoline, distyryl arylene, cyclopentadiene, tetraphenyl butadiene,bisstyryl anthoracene, perylene, phenanthrene, oligothiophene,pyrazoloquinoline, thiadiazopyridine, laminated perovskite,p-sexiphenyl, spiro compound, etc.).

As described above, a great variety of materials and techniques havebeen studied on the light emitting material and device productionprocess of the organic electroluminescence device. However, thesestudies have not yet completely clarified the efficiency where theamount of light can be emitted from such an organic electroluminescencedevice. According to the References (“Major Issues of Organic LEDElements to be Solved and Practical Statistics” edited by the OrganicElectronics Material Research Organization, Bunshin Publishing Co.,mid-1999, P.105-118, and “Chapter 1 Interpretation and Limit of LightEmitting Efficiency” by Tetsuo IZUTSU), optical energy taken out of theorganic electroluminescence device is given in terms of the number ofphotons released for each of electrons or holes running through thedevice. If this is expressed in terms of external quantum efficiency ofelectroluminescence η₁₀₀(ext), the following relationship is known tohold:η₁₀₀(ext)=η_(ext)×η₁₀₀(int)=η_(ext)×[γ×η_(r)×η_(f)]  (1)where η₁₀₀ (int) is an internal quantum efficiency representing thenumber of photons released for each of the electrons or holes runningthrough the device inside the device, and η_(φ)(ent) denotes theefficiency of discharging, out of the device, the light produced insidethe device after having been reduced by reflection or absorption on thedevice boundary. γ shows the charge balance equivalent to the ratio ofthe numbers of the electrons and holes injected inside the device, andη_(r) indicates the singlet exciton generation efficiency denoting theratio of emitting the i-term exciton contributing to light emitted fromthe injected electric charge. η_(f) denotes light emitting quantumefficiency representing the ratio of emitting light and deactivating inthe singlet exciton.

The external quantum efficiency η₁₀₀ (ext) equivalent to the amount oflight emitted out of the device can be broadly classified into three,that is, η_(r) and η_(f) determined by the properties of the lightemitting material itself, γ determined by the ratio of injecting theelectrons and holes into the device, and η(ext) determined by the devicestructure. η_(r) and η_(f) are efficiencies related to the physicalproperties of the light emitting material itself and are uniquelydetermined by the light emitting material. γ is the amount determined bythe electrical potential difference between the electrode and organiclayer adjacent thereto, the boundary potential and the ease of movementof the electrons and holes in the organic layer. It is an efficiencyuniquely determined by the physical properties of the electrode materialand device internal organic material. Of these factors, the chargebalance γ≦1. The singlet exciton generation efficiency η_(r) is said tobe the electrical charge spin η_(r)≦0.25. Light emitting quantumefficiency η_(r)<1 except in the 10 super-radioactive process.Therefore, the portion of the factor determined by the organic materialinside the device and electrode material (the portion [γ×η_(r)×η_(f)] inFormula (1)) is said to be 0.25 or less. On the other hand, according tothe Reference (Greenham, R. H. Friend, D. D. C. Bradley. Adv. Mater. 6,491 in 1994), the discharge efficiency is determined by the reflectionand refraction of classical optics. Assuming that the refractive indexof the light emitting layer is “n”, it is given by the followingequation:η_(ext)=1/(2n ²)   (2)

The refractive index of the light emitting layer of many organicelectroluminescence devices or the glass substrate holding them is about1.6. Thus, η_(ext)=0.2. From the above discussion, the external quantumefficiency of the external electroluminescence is η₁₀₀(ext)≦0.2×0.25=0.05, and the external quantum efficiency is said to be5% at most.

To put the organic electroluminescence device to commercial use, it isessential to improve the external quantum efficiency. The externalquantum efficiency of the above-mentioned conventional organicelectroluminescence device has an upper limit, so the development of anorganic electroluminescence device having different functions iscurrently under way. One of the methods is to improve the light emittingquantum efficiency singlet exciton generation efficiency fir of thelight emitting material itself. In the conventional charge injection andre-combination process, singlet exciton occurs at the ratio of 0.25, andtriplet exciton occurs at the ratio of 0.75. By contrast, the tripletexciton is converted to a singlet exciton by spinning in a reversedirection through an inter-item intersection resulting from thespin/orbital angular moment interaction of the organic light emittingmaterial containing heavy metal, or the triplet exciton that hasoccurred is converted into a singlet exciton through mutual collision oftriplet excitons enclosed in the nano-level range, thereby increasingthe ratio of the exciton making contribution to light emission. As thematerial having such a new exciton generation mechanism, an organicelectroluminescence device capable of high-efficiency light missionthrough the use of factris (2-phenylpyridine) iridium [Ir(ppy) 3] isintroduced in Reference (M. A. Baldo, S. Lamansky, P. E. Burrows, M. E.Thompson, and S. R. Forrest, Appl. Phys. Lett. 75, 4-6 in 1 999).

Another method is intended to improve the external quantum efficiencyoutside the device by improving the discharge efficiency η_(ext).Namely, a uniform thin film structure without crystal segregation hasbeen considered essential for the production of the organicelectroluminescence device. In this case, the organic light emittingmaterial constituting the light emitting layer is random-oriented interms of space. So light has been emitted isotropically in alldirections inside the device. By contrast, a means of controlling thelight emitted in the direction parallel to the light emitting surface ofthe device and increasing the light emitted in the vertical direction isdescribed in the Reference (Japanese Patent Laid-Open 40413/1992) whichdiscloses an organic electroluminescence device having a light emittinglayer comprising molecules uniaxially oriented, for example, by therubbing method.

According to the Reference (Japanese Patent Laid-Open No. 102783-1999),in the organic electroluminescence device produced by forming a lightemitting layer in the dry process in a vacuum and by orienting theorganic molecules constituting the light emitting layer parallel to thelight emitted surface by photoisomerization reaction, an anisotropiclight emitting characteristic was similarly obtained inside the lightemitting layer. However, improvement of the discharge efficiency byorientation is not specifically described in these References. Only theReference (Japanese Patent Laid-Open NO. 102783/1999) describes thatlight emitting efficiency outside the device was improved about 1.6times from 0.51 m/W to 0.81 m/W.

In the earlier Reference (M. Hamaguchi and K. Yoshino, Jpn, J. Appl.Phys. Vol. 34, P. L712, in 1995), detailed measurements were made on thelight emitting anisotropy and discharge efficiency of the orientedorganic electroluminescence device. According to FIG. 1 thereof, aremarkable difference in the amount of light to be discharged isobserved in the direction parallel to the orientation and the directionvertical thereto. By contrast, no marked difference in the amount of thedischarged light is observed between the oriented sample andnon-oriented sample.

As described above, methods of improving the light emitting efficiencyover the previous level are being studied for the organicelectroluminescence device. Since many such factors are included, nodefinite guideline has been established as yet.

To put such an organic electroluminescence device into practical use, itis essential to improve the external quantum efficiency. There is anupper limit to the external quantum efficiency of the above-mentionedconventional organic electroluminescence device. One of the methods isto improve the singlet exciton generation efficiency η_(r) of the lightemitting quantum efficiency of the light emitting material itself, andto improve the external quantum efficiency outside the device byimproving the discharge efficiency η_(ext). Of these, the latterproposal is associated with the improvement of discharge efficiencyη_(ext). It is intended to provide a more extensive efficiencyimprovement.

Namely, when the discharge efficiency of the conventional organicelectroluminescence device was analyzed, isotropic light emission insidethe light emitting layer was the basis for logical analysis. Improvementof discharge efficiency was suggested when molecules were orienteduniaxially or in parallel to the light discharge plane. But there was noclear description of the specific degree of orientation, its orientationor the correlation between the related direction of light emission andthe structural orientation direction of the molecules. Therefore, therelationship between the molecule orientation direction and orientationdirection to provide the optimum discharge efficiency was notnecessarily clear. For this reason, it was not possible to performabsolute quantitative design regarding the obtained spatial orientationfor light emission.

Furthermore, systematic and concrete study has not been made to clarifythe relationship among the polarization and double refraction of thelight emitting component itself caused by forming the state ofanisotropic light emission, changes in the ease of movement of relatedelectrons and holes, and the state of the boundary between the deviceand the outside of the device to discharge their light emittingcharacteristics out of the device in the final phase. In addition, nostudy has been made on the relationship with various intermediate layersexisting between the light emitting layer and device boundary. Theimpact of these factors upon the emission spectrum distribution has notbeen studied. For this reason, no sufficient achievement has been madein terms of improvement of the external quantum efficiency based on thedischarge efficiency improvement technique of conventional devices.

A control method by a fine resonator having a resonance length on theorder of a wavelength is known as a orientation control means for anemission pattern. For example, the Reference (S. Tokito, Y. Taga and T.Tsutsui, Synthetic Metals, Vol 91, P. 49, 1997) includes a report on afine resonator structure type organic electroluminescence device wheretris(8-quinolinolato) aluminum (Alq3) is used as a light emittingmaterial, and MgAg is employed for the electrode cum reflector on theback side, ITO for the electrode on the light discharge side, and(SiO₂/TiO₂) derivative multi-layered film for the translucent mirror onthe light discharge side. FIGS. 3 and 4 show that the directivity of theemission pattern is improved by the introduction of a fine resonatorstructure. When the light intensity is “1” on the front of the lightemitting device, the radiation angle where the light intensity isreduced to a half is about 60° when there is no fine resonancestructure. By contrast, the light intensity is reduced to about 20° whena fine resonance structure is used, according to this Reference.However, in this method, the directivity of radiation differs accordingto the light wavelength, and there is a big change in the spectrumdepending on the angle of view. At the same time, the directivity isincreased extremely. So when it is used as a display for an organicelectroluminescence device, there has been a problem that the angle ofthe field is reduced.

Another method is disclosed in the Reference (Japanese Patent Laid-OpenNo.102783/1999). According to this method, a light emitting layer isformed in vacuum by a dry process, and the organic compound moleculeconstituting said light emitting layer is oriented in parallel to thelight emitting surface, thereby improving the light emitting efficiency.According to this report, the light emitting organic molecule isoriented randomly in three dimensions in the conventional light emittinglayer, and a light emitting efficiency of about 0.2 was the limit.According to this technique, the light emitting efficiency is excellentin the direction vertical to the light emitting surface. In this case,the light emitting molecule may be randomly oriented in two dimensionswithin the surface parallel to the light emitting surface, according tosaid Reference. In this technique, however, when the light intensity onthe front of the light emitting device is “1”, radiation angle where thelight intensity is reduced to a half is still about 20°, as shown inFIG. 3, and the directivity is too high. This has been a problem.

Namely, the optimum comprehensive conditions for the device have notbeen proposed for the overall improvement of the characteristics in anorganic electroluminescence device, such as light emitting efficiency,discharge efficiency, directivity and anisotropy.

Furthermore, there has been no proposal on the image display system andconfiguration method thereof using the effects specified said organicelectroluminescence devices which cannot been observed in other flatpanel displays, or on the method of use, for example, in videodistribution services based on said system which cannot be observed inthe conventional video or sound broadcasting services.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using said device,characterized by allowing both positive and negative electrical chargesto be injected and transported, allowing light to be emitted byre-combination between holes and electrons generated by the positive andnegative electrical charges, and comprising a light emitting substancewhich emits light due to re-combination contained in the organicelectroluminescence device or a fluorescent substance capable ofemitting a secondary light upon receipt of light from the light emittingsubstance.

The organic electroluminescence device is characterized in that at leastone light emitting substance or fluorescent substance capable ofemitting light anisotropically inside the light emitting substance layeris provided, and the majority of the transition dipole moment of themolecular skeleton related to light emission in the moleculesconstituting the light emitting substance or fluorescent substance isdistributed at an angle from 0 to 70 deg. with respect to the directionof the normal to the light discharge plane in the layer to which thesubstance belongs.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that light discharged out of theanisotropically-light emitting substance layer has a polarizingcharacteristic.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that a first class intermediate layer iscontained outside the anisotropically light-emitting substance layerbetween the layer and the boundary for discharge of light out of theorganic electroluminescence device, and the refractive index of theintermediate layer of the first class is lower than that of theanisotropically light-emitting substance layer or refractive index ofthe first class intermediate layer and does not exceed 1.42.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the thickness of the first classintermediate layer has the length greater than the wavelength of thelight discharged.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the orientation exhibiting themaximum light intensity in the distribution of the intensity of lightdischarged out of the anisotropically light-emitting substance layer islocated within the range from 0 to 60 deg. with respect to the normalaxis of the boundary for discharging light out of the device.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that light is anisotropically emittedfrom the fluorescent substance capable of emitting a secondary lightupon receipt of light from the light emitting substance.

Another embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using said device,characterized by allowing both positive and negative electrical chargesto be injected and transported, allowing light to be emitted byre-combination between holes and electrons generated by the positive andnegative electrical charges, and comprising a light emitting substancewhich emits light due to re-combination contained in the organicelectroluminescence device or a fluorescent substance capable ofemitting a secondary light upon receipt of light from the light emittingsubstance; wherein the organic electroluminescence device andphotoelectron device using said device are further characterized in thata second class intermediate layer is contained outside thelight-emitting substance layer between the layer and the boundary fordischarge of light out of the organic electroluminescence device, anddistribution of the intensity of light discharged out of the substancelayer is increased after passing through the second class intermediatelayer.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the second class intermediate layeris capable of scattering light or diffusing the optical path.

Still another embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using said device,characterized by allowing both positive and negative electrical chargesto be injected and transported, allowing light to be emitted byre-combination between hole and electron generated by the positive andnegative electrical charges, and comprising a light emitting substancewhich emits light due to re-combination contained in the organicelectroluminescence device or a fluorescent substance capable ofemitting a secondary light upon receipt of light from the light emittingsubstance; wherein the organic electroluminescence device ischaracterized in that a third class intermediate layer is locatedoutside the light-emitting substance layer in the direction opposite tothe boundary for discharging light out of the organicelectroluminescence device, and the light taken out of the substancelayer to the third class intermediate layer by the third classintermediate layer is reflected.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the light taken out of thesubstance layer to the third class intermediate layer by the third classintermediate layer is reflected in a direction other than the directionof regular reflection.

A further embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using said device,characterized by allowing both positive and negative electrical chargesto be injected and transported, allowing light to be emitted byre-combination between hole and electron generated by the positive andnegative electrical charges, and comprising a light emitting substancewhich emits light due to re-combination contained in the organicelectroluminescence device or a fluorescent substance capable ofemitting a secondary light upon receipt of light from the light emittingsubstance; wherein the organic electroluminescence device ischaracterized in that the light emitting substance layer is separated bya partition having a contact surface which is not parallel to theboundary for discharging light out of the organic electroluminescencedevice, and the partition is formed along the height crossing the lightemitting layer or is formed on a layer or substrate other than the lightemitting layer.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the partition viewed from thedischarge boundary is polygonal and at least two sides of the partitionforming the polygon are parallel.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that at least one of a pair of parallelpartitions forming the polygon has a length equivalent to one fourth totwo fourths of the wavelength of the emitted light.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the partition viewed from thedischarge boundary is circular.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the diameter of the circularpartition is equal to length equivalent to one fourth to two fourths ofwavelength of the emitted light.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the contact surface that is notparallel to the light discharge boundary of the partition can reflect orbend the light taken out of the light emitting substance layer.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that reflection by the partition is notregular reflection.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that a pair of the fourth classintermediate layers becoming one or more pairs of resonator mirrorsholding the substance layer in-between is contained outside the lightemitting substance layer, and the distance between the pair of thefourth class intermediate layers is an integral multiple of a lengthequivalent to one fourth to two fourths of wavelength of the emittedlight.

A still further embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using said devicecapable of allowing both positive and negative electrical charges to beinjected and transported, allowing light to be emitted by re-combinationbetween holes and electrons generated by the positive and negativeelectrical charges, and comprising a light emitting substance whichemits light due to re-combination contained in the organicelectroluminescence device or a fluorescent substance capable ofemitting a secondary light upon receipt of light from the light emittingsubstance; wherein at least one light emitting substance or fluorescentsubstance capable of emitting light anisotropically inside the lightemitting substance layer is provided, and the majority of transitiondipole moment of the molecular skeleton related to light emission in themolecules constituting the light emitting substance or fluorescentsubstance is distributed at an angle from 0 to 70 deg. with respect tothe direction of the normal to the light discharge plane in the layer towhich the substance belongs.

The organic electroluminescence device is further characterized in thata second class intermediate layer is contained outside theanisotropically light-emitting substance layer between the layer and theboundary for discharge of light out of the organic electroluminescencedevice, and the distribution of the intensity of light discharged out ofthe substance layer is increased after passing through the second classintermediate layer; or a third class intermediate layer is locatedoutside the light emitting substance layer in the direction opposite tothe boundary for discharge of light out of the organicelectroluminescence device, and the light discharged out of thesubstance layer to the third class intermediate layer by the third classintermediate layer is reflected; or, the light emitting substance layeris separated by a partition having a contact surface unparallel to theboundary for discharging light out of the organic electroluminescencedevice, and the partition is formed along the height crossing the lightemitting layer or is formed on a layer or substrate other than lightemitting layer.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the partition is formed in thedirection parallel to the direction of polarization having occurredinside the device film surface but not in the direction vertical to thedirection of polarization.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the direction showing one half ofthe luminance in the direction of 0 deg. with respect to the directionof the normal to the light discharge plane is 40 deg. or more.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the light emitting substance layercontains an organic compound of ionic nature.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that an organic compound having thestructure of Chemical Formula 1 contained therein.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that light is taken out of the boundaryopposite to the substrate with respect to the light emitting substancelayer.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the organic electroluminescencedevice is formed on the substrate where an amorphous silicon thin filmtransistor or polycrystalline silicon thin film transistor is formed, oron the substance where an organic thin film transistor is formed.

The organic electroluminescence device and photoelectron device usingsaid device is characterized in that the organic electroluminescencedevice is integrated after having been formed separately from thesubstrate where an amorphous silicon thin film transistor orpolycrystalline silicon thin film transistor or a substrate where theorganic thin film transistor is formed.

A still further embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using the devicecharacterized by a three dimensional display, which can be viewed by theuser wearing glasses which allow the light emitted from the organicelectroluminescence device to reach each of the right and left eyes ofthe user separately in conformity to the difference in polarization, anda three-dimensional display viewing system wherein three-dimensionalvideo information is filmed to provide the three-dimensional display,and image processing is performed, whenever required, so that theinformation is converted into recording or broadcasting media which aresent to the user.

A still further embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using the devicecharacterized by a three dimensional display which can be viewed by theuser wearing glasses which allow the light emitted from the organicelectroluminescence device to reach each of the right and left eyes ofthe user separately in conformity to the difference of polarization, andan encryption display viewing system wherein signals are divided toensure that the normal image is viewed by the user without said glasses,but different information is displayed for the user wearing said glassesdue to a difference in polarization.

A still further embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using the devicecharacterized by a display viewing system wherein normal displayviewing, three-dimensional display viewing and encryption displayviewing can be separated on one display screen.

A still further embodiment of the present invention provides an organicelectroluminescence device and photoelectron device using the devicecharacterized by a display viewing system; wherein normal displayviewing, three-dimensional display viewing and encryption displayviewing can be selectively used according to an agreement between theimage provider and the user, and the function of the decoder to permitreading by the user can be switched in conformity with said selection,or the decoder selection and time period can be changed according to theagreement as required even if the recording or broadcasting mediasupplied by the image provider are the same. Furthermore, the agreementcan be signed up, modified or canceled by controlling the setupconditions of said display viewing system of the user through theInternet whenever required.

The organic electroluminescence device allows the holes to be injectedfrom the anode electrode and the electrons to be injected from thecathode electrode for the light emitting layer, including the organiclight emitting molecules, and permits light to be emitted byrecombination of the holes and electrons inside said light emittinglayer, where the layer can be either single or multiple layer. Inaddition to the organic light emitting molecule which emits light byrecombination of a hole and electron, said light emitting layer cancontain a fluorescent substance (or phosphorescent substance) whichabsorbs the light emitted from said organic light emitting molecule toemit another beam of light. Furthermore, said light emitting layer cancontain a hole transport substance or electron transport substance whichfacilitates movement of the hole or electron inside said light emittinglayer. Said light emitting layer can also incorporate a capturingsubstance or electron capturing substance which captures the hole orelectron at a specific spatial position or reduces the transportability.Furthermore, said organic light emitting molecule, fluorescent substance(or phosphorescent substance), hole transport substance, electrontransport substance, hole capturing substance and electron capturingsubstance can be incorporated in one and the same layer, or can bedispersed and contained in different layers. Even when theseconstituting substances are separated, multiple layers containing themare formed, and such multiple layers are collectively called a lightemitting layer in the description of the present invention.

A hole injection layer or electron injection layer to improve the holeor electron injection efficiency may be installed between said lightemitting layer of the present invention and said anode or said cathodeto inject holes or electrons to said light emitting layer.

Substrates to hold said light emitting layer, anode, cathode, holeinjection layer and electron injection layer may be installed. Otherintermediate layers may be installed whenever required. Suchintermediate layers include a reflection mirror to modulate lightreflection characteristics, a partial transmission mirror, a filter toallow specific light to pass through, a light switch to adjust theongoing light timing, a wavelength plate to adjust light phasecharacteristics, a dispersion plate to disperse light in the ongoingdirection, and a protective film to prevent device constitutingsubstances from being deteriorated by external light, heat, oxygen orwater. These intermediate layers can be installed between said lightemitting layer, anode, cathode, hole injection layer, electron injectionlayer and substrate or on their outside, as required, based on thespecifications which protect device characteristics againstdeterioration. Of these layers, the layer as the top surface from whichlight is discharged out of the organic electroluminescence device willbe called a top discharge layer.

The transition dipole moment in the description of the present inventiondenotes the transition moment as a non-diagonal element out of thetransition dipole matrix elements constituting the electric dipoletransition by molecular light. Its absolute value is proportional tooscillator intensity, and defines the directions of light radiation andpolarization. To put it more specifically (according to “UnabridgedDictionary of Applied Physics” edited by the Japan Society of AppliedPhysics, Ohm Publishing Co., Ltd., 1998), the term electric dipoledenotes a pair of electrical charges having different symbols located acertain distance away from each other. By contrast, the transitiondipole matrix element appears when calculating the transitionprobability between quantum states accompanied by dipole radiation. Itdenotes the matrix element of the initial state φ_(i) and final stateφ_(f) of the dipole moment as an operator.P _(fi) =<φf|p|φi>

Transition between the electron states having different initial andfinal states (i.e. φi≠φf is called the transition moment. Assume in thiscase that the electron mass is m_(o), the frequency of transition energybetween electron states is ω_(fi), and the value obtained by dividingthe black Planck's constant by 2π is η. Then the oscillator intensity isexpressed by the following formula:${Ffi} = {{\frac{2}{m_{0}n\quad\omega_{fi}}{{{< \varphi_{f}}❘p}}\varphi_{i}} > 2}$

The electroluminescence material which can be used in accordance withthe present invention includes various metal complex type light emittingmaterials (8-quinolinol, benzooxazol, azomethine, flavone, etc. asligand, and Al, Be, Zn, Ga, Eu, Pt, etc. as central metal) andfluorescent pigment based light emitting material (oxadiazole,pyrazoline, distyryl arylene, cyclopentadiene, tetraphenyl butadiene,bisstyryl anthoracene, perylene, phenanthrene, oligothiophene,pyrazoloquinoline, thiadiazopyridine, laminated perovskite,p-sexiphenyl, spiro compound, etc.). Or, it is also possible to usevarious types of high molecule materials (polyphenylene vinylene,polyvinyl carbazole, polyfluorene, etc.) as the light emitting material,or to use the non-light emitting high molecular material (polyethylene,polystyrene, polyoxyethylene, polyvinyl alcohol, polymethylmethacrylate, polymethyl acrylate, polyisoprene, polyimide,polycarbinate, etc.) as a matrix, thereby blending and copolymerizingvarious types of light emitting materials or fluorescent materials. Itis also possible to use various organic holes or an electron transportmaterial (triphenylamine, etc.) as an intermediary. Furthermore, varioustypes of hole or electron injection layers (e.g. Li, Ca, Mg, Cs, CuPc,etc.) can be used as the intermediary. Materials can be used inconformity to the device configuration as required. The preferredcompound among various types of said organic electroluminescencematerial is organic compound having a transition dipole moment with agreat light emitting power in the molecular structure capable ofanisotropic light emission. It is preferred that a molecular structurewhich facilitates control of the orientation state of the part of themolecule or molecular skeleton is present in the molecule skeletonitself having the transition dipole moment related to such lightemission or in the part of the molecule other than said molecularskeleton.

An organic electroluminescence device according to the present inventioncan be created using various thin film formation techniques, such as aspin coating method, coating method, casting method, sputtering method,vacuum evaporation method, molecule beam vacuum evaporation method,liquid phase epitaxial method, atomic layer epitaxial method, rollmethod, screen printing method, ink jetting method, field polymerizationmethod, rubbing method, spraying method, water surface developmentmethod and Langmuir-Blodgett film method.

The following methods can be used to control orientation of thetransition dipole moment related to said light emission with a desiredorientation. There is a spin coating method based on the centrifugalforce during film formation, an axial spin coating method to turn thesubstrate about its rotary axis, a specific direction spraying orhigh-speed substrate movement/rotation method, a pull-put method, aninjection method, a roll orientation method where simultaneousorientation is carried out in the possible film forming process byorientation of the molecular skeleton including a specified transitiondipole moment in a specific direction in the film formation process orother molecular skeletons under greater orientation restrictions, a spincoating method after formation of thin film, a rubbing method, anelectric field application method, a magnetic field application method,an optical orientation method and a thermal annealing method whereorientation is carried out after film formation.

In order to promote orientation during or after film formation, it isalso possible to use a crystalline substrate where the substrate itselfhas an orientation restricting force, an oriented film coated substrateand substrates provided with physical or chemical surface treatment.Furthermore, the molecular skeleton in the compound suited toorientation treatment is preferred to exhibit liquid crystal propertiesin the orientation process. It is also effective to fix the state oforientation by cooling the sample below the glass transition temperatureafter orientation or by formation of new chemical bondage betweenmolecules through reaction by light and heat.

Furthermore, the substrate used can also be a substrate comprising suchinorganic substances as glass, silicon and gallium arsenide, a substratecomprising such organic substances as polycarbonate, polyethylene,polystyrene, polypropylene and polymethyl methacrylate, or a substratecomprising a combination of organic and inorganic substances. Thesesubstrates can be formed by grinding and injection molding after thematerial is taken out of the matrix. The partition and the second, thirdor fourth class intermediate layer according to the present inventioncan be formed inside the substrate or on the surface thereof in theprocess. After that, the intended organic electroluminescence layer canbe formed. In addition, to control the state of light emission, it ispossible to use the substrate where a thin film transistor is formed. Anorganic electroluminescence layer can be formed on the substrate wheresuch a thin film transistor is formed. Or it is also possible toseparately produce the substrate where a thin film transistor is formedand the substrate where an organic electroluminescence layer is formed.Then, these substrates can be integrated into one piece.

The organic electroluminescence device of the present invention allowsuse of various precision processing techniques in order to produce theoptical device structure required in the device formation process. Suchprocessing technique includes precision diamond cutting, laser cutting,etching, photolithography, reactive ion etching and focused ion beametching. It is also possible to lay out multiple pre-processed organicelectroluminescence devices, to create multi-layered structures thereof,to connect them by an optical waveguide or seal them in the currentstate.

The device can be stored in a vessel filled with inert gas or liquid. Itcan also be provided with a cooling or heating mechanism to adjust theworking environment. The vessel can be made of such metals as copper,silver, stainless steel, aluminum, brass, iron and chromium, theiralloys, composite materials formed by dispersing such metals in highmolecular materials such as polyethylene and polystyrene, and ceramicmaterials. In addition, a heat insulating layer, foamed styrene, porousceramic, glass fiber sheet and paper can also be used. Especially,coating can be provided to prevent dew condensation. The inert liquid tobe filled inside can be water, heavy water, alcohol, wax of a lowmelting point, mercury and the liquid mixture thereof. Inert gas to befilled inside can be helium, argon, nitrogen, etc. A desiccator can beplaced to reduce humidity in the vessel.

The organic electroluminescence device of the present invention can betreated for improvement of its external appearance, characteristics andservice life after formation of the product. Such post-treatmentincludes thermal annealing, application of radiation, irradiation withan electron beam, light, radio waves, magnetic beam and supersonicwaves. Furthermore, the organic electroluminescence device can be madecomposite in various ways, for example, by adhesion, fusion,electrodeposition, vacuum evaporation, crimping, dyeing, formation ofmelting, kneading, press molding, coating, and other appropriate meansin conformity to particular applications or purposes.

The organic electroluminescence device of the present invention can bepackaged with a high density at a position close to the electroniccircuit for drive, and can be integrated with the interface or antennafor exchange of signals with the outside.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) are diagrams which show examples of the basicstructure of an organic electroluminescence device according to thepresent invention;

FIGS. 2(a) and 2(b) are diagrams illustrating the coordinate system usedto define the spatial relationship between the molecule skeleton axis,the transition dipole moment and the device discharge plane of the lightemitting material used in the organic electroluminescence deviceaccording to the present invention;

FIG. 3 illustrates a series of graphs which represent the relativeamount of ongoing light to the device discharge with respect to a givenangle of the transition dipole moment of the light emitting materialused in the organic electroluminescence device according to the presentinvention;

FIG. 4(a) is a diagram and FIG. 4(b) is a series of graphs which showthe relationship between optics and the p-polarization transmittance ofthe discharge angle when light is directly discharged to the outsidefrom one of the light emitting layers of the organic electroluminescencedevice according to the present invention;

FIG. 5 is a series of graphs which show the relative amount of ongoinglight to the device discharge plane with respect to a given angle of thetransition dipole moment of the light emitting material used in theorganic electroluminescence device according to the present inventionwhen light is directly discharged to the outside from one of the lightemitting layers;

FIG. 6 is a series of graphs which show the relative amount of ongoinglight in a manner similar to that of FIG. 5 where the internalrefractive index is greater;

FIG. 7 is a diagram which show an optical relationship when anintermediate layer is provided between the light emitting layer anddevice exterior;

FIG. 8 is a series of graphs which show the relative amount of ongoinglight to the device discharge when an intermediate layer is providedbetween the light emitting layer and device exterior;

FIGS. 9(a), 9(b) and 9(c) are diagrams which show the relative amount ofongoing light to the device discharge plane with respect to averagedistribution when there are multiple transition dipole moments of thelight emitting material used in the organic electroluminescence deviceaccording to the present invention;

FIGS. 10(a) and 10(b) are diagrams of the electrode pattern of thedevice used to verify performances of the organic electroluminescencedevice according to the present invention;

FIGS. 11(a), 11(b), 11(c) and 11(d) are diagrams which represent thestructural formula of the compound used to verify the performances ofthe organic electroluminescence device according to the presentinvention;

FIGS. 12(a), 12(b) and 12(c) are diagrams which indicate the structureof the spin coater used to verify performances of the organicelectroluminescence device according to the present invention;

FIGS. 13(a) and 13(b) are graphs of the device absorption spectrum andpattern of the degree of orientation, respectively, created to verifyperformances of the organic electroluminescence device according to thepresent invention;

FIGS. 14(a) and 14(b) are a diagram and a graph, respectively, showingthe emission pattern of the device created to verify performances of theorganic electroluminescence device according to the present invention;and

FIGS. 15(a) to 15(f) are diagrams showing examples of the secondintermediate layer to improve the radiation angle of the organicelectroluminescence device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description of various embodiments of the organic electroluminescencedevice according to the present will be described invention withreference to the drawings and various tables.

First Embodiment

First, the light emitting characteristics of the light emittingmolecules contained in the organic electroluminescence device as a basicfeature of the present invention, or the fluorescent molecules whichemit secondary light upon receipt of light from the light emittingmolecule, will be described with reference to the design guideline ofthe device to be obtained.

For the organic electroluminescence device according to the presentinvention, the following is defined as the most important aspect withrespect to the device design. Namely, the organic electroluminescencedevice allows positive and negative electrical charges to be injectedand transported, is capable of emitting light by recombination betweenthe holes and electrons generated by said positive and negativeelectrical charges, and is capable of containing a light emittingsubstance which emits light by recombination included in said organicelectroluminescence device, or a fluorescent substance capable ofemitting secondary light upon receipt of light from the light emittingsubstance; wherein the light emitting organic electroluminescence deviceand photoelectron device using said device emit light anisotropicallyinside said light emitting substance layer, and the transition dipolemoment related to emission of said light of at least one light emittingsubstance or fluorescent substance in the layer to which the substancebelongs is distributed in the direction normal to the light dischargeplane at angles between 0 and 45 degrees. This will be described belowwith reference to the following drawings and tables.

FIGS. 1(a) and 1(b) show the basic structure of the organicelectroluminescence device according to the present invention. FIG. 1shows the device structure where the light coming from the orientedlight emitting layer (4) formed on the transparent substrate (7) isdirected to the substrate side. More specifically, the transparent anode(6), hole injection layer (5) and oriented light emitting layer (4) areinstalled on the transparent substrate (7) one on top of another.Further, an electron injection layer (3), cathode (2) and protectivelayer (1) are formed on them. A top discharge layer (8) is formed belowthe transparent substrate (7). The light emitting layer (4) which emitslight in response to the ejection of a hole from the anode and anelectron from the cathode and their recombination is preferred to have athickness of 10 nm or more. It forms a thin film layer containing theorganic light emitting molecule.

FIG. 1(b) shows a device structure when the light from oriented lightemitting layer (12) formed on the substrate (15) without transmission ismoved to the side opposite to the substrate. More specifically, cathode(14), electron injection layer (13), oriented light emitting layer (12),hole injection layer (11), transparent anode (10), and top dischargelayer (9) are disposed on the substrate (15) in that order.

The light emitting layer (4) which emits light in response to ejectionof a hole from the anode and an electron from the cathode and theirrecombination is preferred to have a thickness of 10 nm or more. Itforms a thin film layer containing the organic light emitting molecules.In this case, the top discharge layer (9) performs the function of theprotective layer (1), which is omitted. Furthermore, cathode (2) alsoserves as a reflection mirror.

In FIG. 1(a) and FIG. 1(b), the lamination order of cathode, electroninjection layer, light emitting layer, hole injection layer and anodecan be reversed. In that case, however, the material must be changed toensure that the cathode or anode on the side of the top discharge layeris transparent.

The material must also be changed to ensure that the anode or cathode onthe opposite side performs the functions of a reflection mirror.

Regarding the basic configuration in the present invention, it isimportant that the dimensions are designed so that the followingrelationship holds between the angular relationship between theorientation of the transition dipole moment of said organic lightemission molecule related to light emitting and the direction normal tothe light discharge plane of said organic electroluminescence device,and the thickness of the related layer. FIG. 2(a) and FIG. 2(b) show theorientational relationship of said organic electroluminescence moleculeand light discharge plane for this explanation. FIG. 2(a) shows theorientational relationship between the transition dipole moment (17) ofsaid organic electroluminescence molecule (16) and the molecular axis.FIG. 2(b) defines the angular relationship between said organic lightemitting molecule (16′) and its transition dipole moment (17′), and thedirection normal to the light discharge plane of said organicelectroluminescence device (18).

As shown in FIG. 2(a), if the orientational axes of the organic lightemitting molecule in structure are Mx, My and Mz, the orientational axiscan be defined uniquely by the molecular structure in the light emittinglayer, generally. (In this case, the internal rotation of thesubstituent in the organic thin film, etc.) are ignored. By contrast,the direction of transition dipole moment related to light emissionvaries according to which light emission level is used. Generally, thestate of the optimum molecular orientation of the organicelectroluminescence device varies according to which light emissionlevel is used. Therefore, designing the light emitting device requiresdefinition of the direction of this transition dipole moment. Assumethat the direction of the transition dipole moment of the light emissionin question is Dx along the axis, and the direction vertical to the Dxaxis where light is radiated most heavily is along the Dz axis. Theremaining axis on the left hand side in the direction vertical to the Dxand Dz axes is the Dy axis. Furthermore, the direction of the major axisof the light emitting molecule is Mx, and the direction of the minoraxis of the molecule is My. The remaining axis on the left hand side inthe direction vertical to the Mx and My axes is the My axis.

For the symmetrical molecule, the major and minor axes may not always befixed. In such a case, a characteristic symmetrical axis is recommendedto be selected as a main axis. In this way, the light emitted from thelight emitting molecule and light emission spectrum and direction ofradiation can be changed by the selection of the state of excitation inquestion. This makes it possible to determine the optimum molecularorientation direction corresponding to the selected state of excitation.

The following discussion is directed to the case where one organic lightemitting molecule (16′) is contained in the organic electroluminescencedevice (18), as shown in FIG. 2(b). Here the light discharge plane ofthe organic electroluminescence device (18), is assumed to be the topsurface. The direction normal to it is considered the Sz axis, and thedirection where the direction of the transition dipole moment (namely,Dx axis) is subjected to orthographic projection inside the lightdischarge plane is assumed to be the Sx axis. The remaining axis on theleft-hand side in the direction vertical to the Sz axis and the Sx axisis assumed to be the Sy axis. Coordinate axes of the molecularstructure, transition dipole moment and organic electroluminescencedevice are determined in this way. For designing of the most efficientdevice configuration, this is the transition dipole moment where lightis emitted first by electroluminescence. The angle formed by this normaldirection Dz axis and the normal direction of the discharge plane of thedevice Sz axis is θ₁, and the angle formed by the light actuallydischarged out of the device and the normal line Sz of the dischargeplane is θ. The following quantitative description indicates how lightis discharged out of the device in the case of such a molecularorientation, and sets forth the optimum direction of orientation.

Light emitted from one transition dipole moment of a single molecule(electronic field) is expressed as a magnetic field polarized in thedirection of the transition dipole moment given by the harmonicoscillator of the electron polarization formed in an approximatelyexcited state. According to the Reference (P. Meystre and M. SargentIII, “Element quantum optics”, 2nd ed., Springer-Verlag, Berlin, 1991,ISBN3-540-54190-X; Sec. 1-3 Linear Dipole Oscillator), the pointingvector S of the light emitted in this manner (electronic field) is givenby the following formula:$S = \frac{{\mathbb{e}}^{2}v^{2}\cos^{2}\theta}{16\pi^{2}ɛ_{0}c^{3}R^{2}}$where ε₀ denotes the dielectric constant under vacuum, “C” the lightvelocity under vacuum, “R” denotes the distance from the center, “e”denotes the charge of an electron, “u” denotes light frequency, “θ”denotes the angle of harmonic frequency from the normal axis, and “n”denotes a unit vector in the direction of radiation. This means that theemission pattern of the harmonic oscillator is proportional to cos²θ.Assuming that the coefficient inherent to a substance is “k”, then thelight intensity K(θ) in the direction q is given by:K(θ)=k cos²θ.

The following shows a prior calculation of the relationship with thetotal amount of light F_(total) where one molecule inside the lightemitting layer is given: $\begin{matrix}{F_{total} = {2 \times {\int_{0}^{\quad}{\frac{\pi}{2}k\quad\cos^{2}\theta \times 2\pi\quad\sin\quad\theta\quad{\mathbb{d}\theta}}}}} \\{= {{\frac{4\pi\quad k}{3}{\int_{0}^{\quad}{\frac{\pi}{2}k\quad\cos^{2}\theta\quad\sin\quad\theta\quad{\mathbb{d}\theta}}}} = {{{\frac{4\pi\quad k}{3}\left\lbrack {{- \cos^{3}}\theta} \right\rbrack}_{0}\frac{\pi}{2}} = \frac{4\pi\quad k}{3}}}}\end{matrix}$The constant k is erased from the formula, thereby defining the lightintensity K(θ) as:${\therefore{K(\theta)}} = {\frac{3F_{total}}{4\pi}\cos^{2}\theta}$

FIG. 3 shows the dependency of the amount of the light emitted from onemolecule inside the light emitting layer on the ongoing direction of thelight when the total amount of light is standardized. Since the samelight is emitted with respect to one transition dipole moment to theobjects on the upper and lower positions, only the emission pattern fromone side will be described below. FIG. 3 shows the relative amount oflight in the direction of angle e when the transition dipole moment θ₁of the molecule is gradually changed from 0 deg. (transition dipolemoment parallel to the device discharge plane) to 90 deg. (transitiondipole moment vertical to the device is discharge plane). The totalamount of light (integral value over the entire angle of each graph) isthe same in all cases. Actually, the light of the same emission patternis discharged on the opposite side. The organic electroluminescencedevice according to the present embodiment has on the opposite side anelectrode playing the role of a reflection mirror. So this light is alsoreflected and is emitted in the same manner. For the sake of simplicity,however, only the emission pattern on one side will be described below).

First, when θ₁=0 deg., the transition dipole moment becomes parallelwith the light discharge plane. cos²θ dependency is given such that thevalue becomes the maximum in the direction of θ=0 deg. and is 0 in thedirection of θ=90 deg. Then, the orientation of the light emittingmolecule changes. When 0 deg. <θ₁<90 deg. +θ and −θ are present in thedirection of Dx, so [ cos²(+θ₁+θ₄)+cos²(−θ₁+θ)]/2 dependency is given.The intensity in the direction of θ=0 deg. is reduced and the intensityin the direction of θ=90 deg. is increased. When θ=45 deg., the relativeamount of light become the same for all angles of θ. Further, withincrease of θ1, the intensity for θ=0 deg. and the intensity for θ=90deg. are reversed. When θ₁=90 deg., the value is 0 in the direction ofθ=0 deg. and is the maximum in the direction of θ=90 deg. As describedabove, the emission pattern given by the transition dipole moment of themolecule inside the light emitting layer can be obtained uniquely by theorientation direction θ₁.

The following description indicates how to obtain the emission patternwhen light is discharged out of the light emitting layer from such alight emitting layer. FIG. 4(a) shows the optical path where lightentering at an angle θ in discharged from inside the light emittinglayer (19) onto the discharge plane at an angle θ out. Assuming that therefractive index inside is the light emitting layer is “n_(in)” and theexternal refractive index is “n_(out)”, since light polarized in thedirection Dx of the transition dipole moment is emitted, the dependencyof the transmittance on the boundary for the p-polarization is obtained.According to the Reference (J. Tsujiuchi “An Introduction to Optics 1”,Basic Course of Science and Engineering 11, Asakura Shoten, 1979, II. P.5 to 32), we get:$t_{p} = \frac{2\frac{n_{in}}{\mu_{in}}\cos\quad\theta_{in}}{{\frac{n_{out}}{\mu_{out}}\cos\quad\theta_{in}} + {\frac{n_{in}}{\mu_{in}}\cos\quad\theta_{out}}}$$T_{p} = {\frac{n_{out}\cos\quad\theta_{out}}{n_{in}\cos\quad\theta_{in}}t_{p}^{2}}$where “t_(p)” denotes the amplitude transmission coefficient withrespect to p-polarization, “T_(p)” denotes the transmittance withrespect to p-polarization, and “μ_(out)” indicates permeability outsidethe light emitting layer. When a normal dielectric is taken intoaccount, we get μ_(in)=μ_(out)=1. Using this formula, FIG. 4(b) showsthe transmittance when the refractive index inside the light emittinglayer is changed, with respect to the refractive index n_(out)=1 (airrefractive index) outside the light emitting layer.

When θ_(out)>70 deg., the transmittance is gradually reduced under theinfluence of the total reflection inside the light emitting layer. Inthe case of such transmittance characteristics, emission patterns fromthe specific transition dipole moment of one molecule as shown in FIG. 3are shown overlapped in FIGS. 5 and 6. If the tilting angle θ1 isgradually increased from 0 deg., there is a reduction in the intensityat the angle θ close to 0 deg. in a similar manner. However, theintensity at an angle θ close to 90 deg. has a small transmittance, sothere is no increase. Therefore, in the range from 0 deg. to 45 deg.,the maximum amount of discharged light is given by θ=0 deg. at alltimes.

In the range from 45 deg. to 90 deg. the maximum amount of light isgained at the angle θ close to 70 deg. FIG. 4 b shows a case where therefractive index n_(in)=1.4 inside the light emitting layer. FIG. 4 balso shows a case where the refractive index n_(in)=2.0 inside the lightemitting layer. The discharge angle dependency shows a similar trend inboth cases. As the refractive index inside the light emitting layer ishigher, the reflective index on the boundary is higher. Thetransmittance is reduced by that amount.

For example, comparison will be made in the case of θ₁=0 deg. where thelight of the highest intensity can be obtained. When n_(in)=1.4, thetransmittance is 0.97. When n_(in)=2.0, the transmittance is 0.90. Inmany light emitting layers, the refractive index is within the rangefrom 1.6 to 2.0 because of involvement of an organic light emittingmolecule and an electrode. There is no direct contact between the lightemitting layer and the outside air. Therefore, some intermediate layerpresent between the light emitting layer and light the dischargeboundary cannot be ignored.

Thus, as shown in FIG. 7, an intermediate layer (20) is provided betweenthe light emitting layer (21) and light discharge plane, and therefractive index n of the intermediate layer has a value intermediatebetween n_(in) and n_(out). In this case, the discharge efficiency isobtained. According to the Reference (J. Tsujiuchi “An Introduction toOptics II”, Basic Course of Science and Engineering 11, Asakura Shoten,1979, V, PP. 0 to 56), the transmittance of p-polarization in such acase is given by the following formula:$t_{p} = \frac{2P_{in}}{{P_{in}m_{11}} + {P_{in}P_{out}m_{12}} + {P_{out}m_{22}}}$$T_{p} = {\frac{n_{out}\cos\quad\theta_{out}}{n_{in}\cos\quad\theta_{om}}t_{p}^{2}}$${P_{in} = \frac{\sqrt{\frac{ɛ_{0}}{\mu_{0}}}n_{in}}{\cos\quad\theta_{om}}},{P_{out} = \frac{\sqrt{\frac{ɛ_{n}}{\mu_{n}}}n_{out}}{\cos\quad\theta_{out}}},{P = \frac{\sqrt{\frac{ɛ_{0}}{\mu_{0}}}}{\cos\quad\theta}}$$m_{11} = \frac{{\left( {1 + y} \right){\cos\left( {k\quad\Delta} \right)}} + {{i\left( {y - 1} \right)}{\sin\left( {k\quad\Delta} \right)}}}{2}$$m_{12} = \frac{{\left( {1 - y} \right){\cos\left( {k\quad\Delta} \right)}} - {{i\left( {y + 1} \right)}{\sin\left( {k\quad\Delta} \right)}}}{2P}$$m_{21} = {p\frac{{\left( {1 - y} \right){\cos\left( {k\quad\Delta} \right)}} - {{i\left( {y + 1} \right)}{\sin\left( {k\quad\Delta} \right)}}}{2}}$$m_{22} = \frac{{\left( {1 + y} \right){\cos\left( {k\quad\Delta} \right)}} + {{i\left( {y - 1} \right)}{\sin\left( {k\quad\Delta} \right)}}}{2}$${k = \frac{2\pi}{\lambda}},{\Delta = {{nd}\quad\cos\quad\theta}}$$y = {\exp\left\lbrack {- \left( \frac{2{d/n}\quad\cos\quad\theta}{10\lambda} \right)^{2}} \right\rbrack}$where ε₀ denotes the dielectric constant under vacuum, “μ₀” denotes thepermeability under vacuum, “λ” denotes the wavelength of light, “d”denotes the film thickness of the intermediate layer, “i” denotes a unitof an imaginary number, and “y” denotes a variable representing thedegree of coherent distance. This means that an interference effectoccurs inside the intermediate layer if the film thickness of theintermediate layer is less than 10 times the distance of about ten timesthe wavelength.

Based on this formula, the amount of discharged light is obtained asshown in FIG. 8. In order to prevent interruption within the range from0.3 to 0.8 micron, the thickness of the intermediate layer was set to 1mm, and the refractive index of the intermediate layer n was set to 1.5.In this case, when the tilting angle θ₁ is from 0 to 50 deg., theintensity at the angle 0 close to 0 deg. is the maximum at all times.However, the value is decreased gradually as the angle becomes wider.The amount of discharged light itself is also decreased as the tiltingangle is increased. It can be seen, however, that, when the tiltingangle θ₁ is 70 deg. or more, the shape is changed so that the intensityat the angle θ close to 50 deg. is the maximum. It is clear from theabove discussion that the light discharge pattern undergoes acomplicated change as the shape of the transition dipole moment changes.

Since the actual light emitting layer contains a great number ofmolecules, the emission pattern inside the light emitting layer exhibitsan average distribution of the molecular population as compared with thecase of one molecule. This is schematically shown in FIGS. 9(a) to 9(c).

In FIG. 9(a), the transition dipole moments of all the molecules areoriented parallel to the light discharge plane, and the emission patternis the same as that in the case of one molecule. FIG. 9(b) shows thecase where the transition dipole moments of all the molecules areoriented parallel to the light discharge plane, and the orientation isdistributed. In this case, the maximum value appears when θ=0 deg., andthe intensity is decreased as the angle becomes wider. The slope is moregentle when compared with FIG. 9(a). FIG. 9(c) shows the emissionpattern when a complete random orientation is reached as a result offurther increase in the distribution of orientation. It reveals thatlight is emitted at the same intensity in all directions. This emissionpattern is the same as in the case of θ1=45 deg. in FIG. 3.

As described above, when orientation of the transition dipole moment isdistributed, the emission pattern corresponds to the pattern in eitherθ₁=0 deg. or 45 deg. discussed with reference to FIG. 3. Therefore,orientation is distributed mainly in another direction, and the emissionpattern inside the light emitting layer can be represented by theorientation pattern shown in FIG. 3. Therefore, all orientation patternsin the case of multiple molecules are included in the process of findingthe orientation pattern discussed above.

As discussed above, the following two conditions can be given as aguideline for designing an organic electroluminescence device permittingthe most efficient light discharge:

1) The transition dipole moment related to electroluminescence should beoriented to a specific position with respect to the optical dischargeplane of said organic electroluminescence device, without using theorientation axis in terms of the molecular structure.

2) In the actual organic electroluminescence device where anintermediate layer is provided between the device boundary and lightemitting layer, without light being taken directly out of the lightemitting layer, at least said transition dipole moment is preferred tobe within the range from 0 and over up to 70 deg. exclusive.

The discharge efficiency can be optimized by controlling the orientationof the organic light emitting molecules inside the light emitting layerso that these conditions are met.

Second Embodiment

The following description is directed to an example in which a device isformed according to the design guideline for the organicelectroluminescence device specifically shown in the First Embodiment.

Firstly, the following discussion considers the result of forming anorganic field light emitting device based on the configuration given inFIG. 1(a).

Silicon glass (1 mm thick, with a refractive index of 1.51, abbreviatedas “Glass”) was used as the substrate. Au ITO transparent electrode(ITO=indium tin oxide) was formed into a thin film (150 nm thick)according to the sputtering method using a sputtering system (byHitachi, DC magnetron in-line type IS-1515). A circular electrodepattern having a diameter of 1 cm at the central portion was formedaccording to the photo resist method, as shown in FIG. 10(a) (ITO linerresistance: 300 μΩ.cm). Poly(3-octylthiophene) (by Aldrich, with aweight average molecular weight of 142,000, in FIG. 11(a), abbreviatedas “PT”) was spin-coated on it (to a thickness of 5 nm) as a holeinjection layer. It was dried under vacuum after having been air-dried.Spin coating was performed by manual spinner ASS-301 provided by AbleInc. Then, to configure a light emitting layer, polyvinylcarbazole (byAldrich, with a weight average molecular weight of 1,100,000, shown inFIG. 11(b), abbreviated as “PVC”) was spin coated (to a thickness of50nm) as a hole transport layer. It was dried under vacuum after havingbeen air-dried.

Then, it was spin-coated (to a thickness of 20 nm) with the followingsolution: 4,4′-bis[{6-[N,N-bis(2-bydroxyethyl)amino]-4-phenylamino-1,3,5-triazin-2-yl)amino]-2,2′-stilbenedisulfonicacid, disodium salt(Fluostine I by Dojinkagaku, FIG. 11(c), abbreviated as FB”) was used asa light emitting molecule, and a solution was formed by dispersing 5% inpoly (vinylalcohol) aqueous solution (by Wako Junyaku, with an averagedegree of polymerization of 2,000, a weight percent with respect towater of 1:1, FIG. 11(d), abbreviated as “PVA”) as a medium. Thissolution was used for said spin-coating. After air-drying, it was heatedand dried under vacuum. This polyvinylcarbazole layer andpoly(vinylalcohol) layer dispersed with light emitting molecules wereput together to form the light emitting layer for the embodimentaccording to the present invention. However, in order to form the lightemitting layer with the state of orientation changed, the layout of thesubstrate on the spin coater was improved.

As shown in FIGS. 12(a) to 12(c), the substrate holder with differentrotational radius was modified so that the state of random orientationwas maintained at the central portion and a greater centrifugal forceworked in the centrifugal direction at a position further away from thecenter. Such improvement was made to change the degree of orientation.Namely, the degree of orientation was adjusted by the position andnumber of rotations of the substrate on the spin coater.

When the thin film was formed where orientation was not controlled, theholder shown in FIG. 12(a) was used. Where orientation is controlled,the holder shown in FIG. 12(b) was used. In this way, the substrate wasfixed in position by vacuum attraction. The holder to create thecentrifugal sample is configured so that the substrate is sucked andfixed on the O-ring through the arm some distance away from the centerof rotation.

Depending on the system specification, the system is designed to ensurethat multiple substrates can be spin-coated in one operation, as shownin FIG. 12(c). In our system, a maximum of two substrates can bemounted. However, the specification of such a centrifugal spin coater isnot restricted to the present embodiment of this invention.

After formation up to the light emitting layer according to saidprocedures, the spin-coated thin film sample was installed in the vacuumevaporation system (MBE-620-OR by Anerba). Lithium fluoride (LiF byRaremetallix, with a purity of 5N) was subjected to vacuum evaporation(to a film thickness of 2 nm) at the base pressure 1×10⁻⁹ Torr or lessas an electron injection layer. Then, metallic aluminum (Al byRaremetallix, with a purity of 6N) as a cathode was subjected to vacuumevaporation (to a film thickness of 200 nm). When the lithium fluorideand metallic aluminum was subjected to vacuum evaporation, a stainlesssteel mask (0.5 mm thick) with a window to cover the circular pattern ofthe ITO electrode as a substrate was kept installed, as shown in FIG.10(b).

After vacuum evacuation, the sample was taken out of the system, asoldering iron was used to connect an anode wire to the end of the ITOwhere the cathode was not vacuum evaporated, and the cathode wire wasmade to contact the end portion of the cathode portion which did notoverlap with the ITO pattern through silver paste (5063-AB by ArdeckInc.). UV resin was used to provide hardening by ultraviolet rays.

After that, the device was sealed by hardening with epoxy resin over thearea sufficiently covering the upper and lower portions of the devicewhere a pair of electrons were present. This was used as the protectivelayer shown in FIG. 1(a). Then, the light discharge area where a thinfilm of the glass substrate was not formed was cleaned by clothimpregnated with acetone, and fluorine based high molecular Teflon (byduPont, Teflon amorphous fluoropolymer, AF1600s, with a refractive indexof 1.32) was cast in it to form a thin film having a film thickness ofabout 0.1 mm. This was used as the top discharge layer shown in FIG.1(a). The sample formed according to the above-mentioned procedure willbe called a sample Teflon/Glass/ITO/PVC/PT/FB+PVA/LiF/Al.

As a reference sample for the degree of orientation, the referencesample Glass/ITO/PVC/PT/FB+PVA, in which the electron injection layerLiF, cathode Al and top discharge layer Teflon were not formed, was alsomade according to the procedure for forming the above-mentioned sampleTeflon/Glass/ITO/PVC/PT/FB+PVA/LiF/AI. Furthermore, the reference sampleGlass/ITO/PVC/PT, in which the FB+PVA layer of the oriented lightemitting layer was not formed, was also made according to the sameprocedure.

To verify the effect of improvement in discharge efficiency, thereference sample Glass/ITO/PVC/PT/FB+PVA/LiF/AI, in which only the lasttop discharge layer was not formed, was also made according to the sameprocedure.

The following description is directed to the technique of evaluating thecharacteristics of the light emitting device of the organicelectroluminescence device according to the present invention.Orientation of the transition dipole moment related to light emissionwas determined according to the following technique.

(1) Degree of In-Plane Orientation

Using the reference sample Glass/ITO/PVC/PT/FB+PVA and Glass/ITO/PVC/PTfor determining the degree of orientation, the transmission absorbanceAbs with respect to straight polarization of vertical incident light wasmeasured for each reference sample. The straight polarization angle φ inthe light discharge plane was changed, and the direction where maximumabsorbance Abs was gained was assumed as direction Sx. The directionvertical to Sx in the internal side was assumed as direction Sy.Measurement was made by an absorbance meter (Spectrometer 350 byHitachi) at a wavelength ranging from 300 to 800 nm at room temperature.

The degree of orientation OP (θ=0 deg.) for the orientation lightemitting layer FB+PVA was obtained from absorbance Abs (Sx) of tworeference samples in the direction Sx and absorbance Abs (Sy) in thedirection Sy according to the following formula:Abs(θ = 0^(∘), Sx; FB + PVA) = Abs(θ = 0^(∘), Sx, GlassITOPVCPTFB + PVA) − Abs(θ = 0^(∘), Sx; Glass|ITOPVCPY)Abs(θ = 0^(∘), Sy; FB + PVA) = Abs(θ = 0^(∘), Sx, GlassITOPVCPTFB + PVA) − Abs(θ = 0^(∘), Sy; Glass|ITOPVCPY)${{OP}\left( {\theta = {0{^\circ}}} \right)} = \frac{\begin{matrix}{{{Abs}\left( {{\theta = {0{^\circ}}},{{Sx};{{FB} + {PVA}}}} \right)} -} \\{{Abs}\left( {{\theta = {0{^\circ}}},{{Sy};{{FB} + {PVA}}}} \right)}\end{matrix}}{\begin{matrix}{{{Abs}\left( {{\theta = {0{^\circ}}},{{Sx};{{FB} + {PVA}}}} \right)} +} \\{{Abs}\left( {{\theta = {0{^\circ}}},{{Sy};{{FB} + {PVA}}}} \right)}\end{matrix}}$

Herein Abs (θ=0 deg. ;Sx; Glass/ITO/PVC/PT/FB+PVA) indicates theabsorbance of sample Glass/ITO/PVC/PT/FB+PVA with respect topolarization in the direction Sx when incident angle θ=0 deg. Thisdegree of orientation OP (θ=0 deg.) corresponds to the in-plane orderparameter. The value is 1 when orientation is given completely in thedirection Sx, and is 0 when not oriented. The value ranges from 0 to 1in the state of intermediate orientation.

FIG. 13(a) shows the absorption spectrum Abs (θ=0 deg.; Sx; FB+PVA) andAbs (θ=0 deg.; Sy; FB+PVA) of a typical orientation sample. Theabsorption spectrum of this orientation light emitting layer has onepeak of absorption located close to 350 nm. This corresponds to thestate of minimum excitation of the light emitting molecule FB. Thespectrum patterns of Abs (θ=0 deg.; Sx; FB+PVA) and Abs (θ=0 deg.; Sy;FB+PVA) were almost the same; only the intensity radio was different.Furthermore, the determined direction Sx agreed with the direction wherethe centrifugal force of spin coating works.

It has been made clear that the molecular skeleton is oriented in thatdirection. FIG. 13(b) shows the degree of orientation OP(θ=0 deg.)gained from the above formula. It can be seen that the degree oforientation of this absorption band is about 0.66664. This means thatthe orientation of the in-plane light emitting molecule is distributedmainly in the direction Sx.

(2) In-Plane Refractive Index

The in-plane refractive index inside of the light emitting layer wasdetermined by the value measured at the wavelength of 633 nm by an Abberefractometer (by Atago) using a He—Ne laser as a light source, and thedispersion of refractive index obtained by the absorption spectrumobtained in the above-mentioned (1) subjected to Eramers-Eronigtransformation. Direction Sx obtained above was used as a main axis.

(3) Out-of-Plane Orientation

The following method was used to estimate the degree of out-of-planeorientation of the light emitting molecules from the light emittinglayer. For the optical system for this evaluation, light emittingdistribution for photoexcitation was measured with the layout shown inFIG. 14(a). A laser beam was applied to the orientation sample (29) inthe Sx-Sz plane using p-polarization. A measurement was made of theintensity of photoexcitation light emission at the radiation angle φ inthe Sy-Sz plane with respect to the incident angle θ at this time. Inthis case, however, the refractive index of the sample obtained in (2)was used to correct the excitation optical intensity due to thedifference transmittance into the orientation sample by the change ofincident angle. First, for out-of-plane orientation of the lightemitting molecules, the emission intensity after correction was measuredwhen the incident angle θ was gradually changed in the state fixed atthe fixed radiation angle (e.g. θ=30 deg.). In this case, the directionwhere the emission intensity becomes the greatest is the out-of-planedirection Dx of the transition dipole moment related to the lightemission. Further, if there is no θ dependency, there is no orientation.

To ensure effective photoexcitation close to 350 nm corresponding to theminimum excitation level from the absorption spectrum obtained in (1),photoexcitation was provided by triple wave generating light (at awavelength of 355 nm) from a Q-switch YAG laser (DCR-3 by Quantaray). Tochange the incident angle of the excitation light, rotation was givenwith respect to the laser incoming path where the sample substrate onthe goniostate was fixed. At the same time, the sensor of theactinometer was fixed onto the goniostate of another rotary axis tomeasure the spatial distribution of the light emission spectrum. Aspectral radiation illuminometer (Spectro Radiometer USR-40V by UshioDenki) was used as an actinometer to measure the wavelength spectrum andthe optical intensity at each wavelength in one operation. A selectivewavelength filter to prevent mixture of excitation light and a polarizerto adjust the state of polarization were used as required.

FIG. 14(b) shows an example of the generated fluorescent spectrum.(Fluorescent spectrum generated from the substrate was measured in thesame optical system using the reference sample without an orientationlayer, and the effect was then corrected. This will not be explainedbelow). Measurement was made by changing the radiation angle. No changewas observed in the spectrum pattern. The maximum intensity was givenclose to φ=0 deg. It has been made clear that the transition dipolemoment at the time of photoexcitation at 355 nm is distributed centeringon the centrifugal direction in the out-of-plane direction as well.

(4) Electroluminescence Spectrum

The following description concerns the technique of evaluating the lightemission spectrum when current was injected to the organicelectroluminescence device of the present invention, and light isemitted.

Basically, an evaluation was made using the measuring system of spatialdistribution of photoexcitation light emission used in (3), by currentinjection this time, not by excitation by a laser beam.Teflon/Glass/ITO/PVC/PT/FB+PVA/LiF/AI and Glass/ITO/PVC/PT/FB+PVA/LiF/AIwere used as samples. The difference of external emission intensityaccording to the presence or absence of Teflon of the top dischargelayer was also evaluated. The injected voltage was fixed at 10 volts toevaluate the emission intensity at a wavelength of 420 nm, where themaximum value of light emission spectrum was given. For the actinometersensor, the angle θ was changed in the Sx-Sz plane for measurement. Theintensity of θ=0 deg. and θ were changed, and the angle at half theintensity when θ=0 deg. was assumed as a half power angle.

Table 1 shows the result of evaluation made in the above method. Forboth samples, there was an increase in the emission intensity with theincrease in the degree of orientation. The half power angle wasdecreased with the increasing degree of orientation. Even when thedegree of orientation was 0.6, the half power angle was 35°. In thesample with Teflon formed on the top discharge layer, the emissionintensity was increased in all degrees of orientation over that of thesample where Teflon was not formed. TABLE 1 Degree of Emission Halfpower Configuration orientation intensity (dc/m²) angle (° C.)Glass/ITO/PVC/PT/ 0 110 60 FB + PVA/LiF/Al 0.1 120 57 0.2 155 53 0.3 18251 0.4 195 46 0.5 210 40 0.6 230 35 Teflon/Glass/ITO/PVC/ 0 120 61PT/FB + PVA/LiF/AL 0.1 130 58 0.2 165 54 0.3 195 50 0.4 208 41 0.5 22240 0.6 242 34

Third Embodiment

The following results of evaluating the characteristics of the organicelectroluminescence device, based on another material configurationusing the same technique as that of the Second Embodiment, wereobtained.

In the preparation of orientation light emitting layer material FB+PVAused in the Second Embodiment, 3% Disperse Orange 13 (by Alrdich, Formalname; 4-[4-(phenylazo)-1-naphthylazo]pbenol, abbreviated as DO13) oflaser pigment was dispersed to obtain a solution (abbreviated asFB+PVA+DO13). An organic electroluminescence device was formed accordingto the same procedure as that of the Second Embodiment. As a result,electroluminescence was found to be widely distributed at a lightemitting wavelength in the range of 500 to 700 nm. Furthermore, theelectroluminescence was polarizing in the similar manner in thecentrifugal direction, and the state of anisotropic orientation wasformed. The sample (abbreviated as PVA+DO13) obtained by removing the FBfrom the light emitting material was prepared in a similar manner. Anorganic electroluminescence device was formed using a similar procedure,but light emission was not observed in the range of the voltage appliedthis time.

This makes it clear that electroluminescence emitted from the lightemitting material FB was re-absorbed by the pigment DO13, andfluorescent light of longer wavelength was produced by the DO13.

Similarly, an orientation (FB+PVA) layer having half the film thicknessof the Second Embodiment was formed on the light emitting layer. Afterthat, an orientation (PVA+DO13) layer also having half the filmthickness was formed, and electroluminescence with half intensity wasobserved. However, when the orientation (PVA+DO13) layer was formedunder non-oriented conditions where it was formed at the central portionof the spin coater, the broad fluorescent light obtained was found to bepolarized in the centrifugal direction of the (FB+PVA) layer.

Fourth Embodiment

The following description is directed to the means to widen the lightemitting distribution of the organic electroluminescence deviceaccording to the present invention, and the result of studying theeffect of the improvement in the angle of field based on said wideningmeans.

In the organic electroluminescence device according to the presentinvention, as described in the First Embodiment 1, the amount ofdischarged light is increased if light is taken out when light emittingmolecules are arrayed in the optimum direction for the wavelength beingused. However, the discharge efficiency is improved in a specificdirection, but the discharge efficiency in other directions is reduced.Especially when its use for display is considered, concerns arise overpossible reduction in the angle of field characteristics. The followingdescription is directed to the face that the light discharge efficiencyand field of view of the radiation angle can be improved by installationof an adequate intermediate layer between the top discharge layer andthe light emitting layer.

As discussed in the First Embodiment, the direction where the maximumemission intensity is provided at various orientation angles is thedirection normal to the transition dipole moment. If this direction andthe normal to the light discharge plane of the organicelectroluminescence device are parallel to each other, it ensures thehighest discharge efficiency. However, this means a reduced dischargeefficiency in other directions; therefore, some means is preferred to beprovided to widen the angle of field on the way. FIGS. 15(a) to 15(f)show examples of such means. The direction where the dischargeefficiency is improved is the direction normal to the light dischargeplane. FIGS. 15(a) to 15(f) show examples of a means of bending theongoing direction of the light emitted in that direction. FIG. 15(a)shows the second intermediate layer (30) where a dispersion plane isprovided on the plane opposite to the light emitting layer in order tobend the direction in which the light is emitted from the light emittinglayer (31) upward. In this case, the direction of the light emitted inthe normal direction is bent. At the same time, part of the dispersionplane, having a vertical incoming plane, is present for the lightemitted in other than the normal direction. This leads to a reduction incontainment of light by all reflections inside the device, and makes itpossible to take out a greater amount of light. In this case, it ispossible to provide a dispersion plane at the portion adjacent to thelight emitting layer (31), but this requires the uneven spots to beprovided on the plane of the light emitting layer. This makes itdifficult to perform uniform electrical charge injection. At the sametime, it becomes more likely to be affected by multiple reflection andothers. Therefore, a distance of 10 times or more of the lightwavelength is preferred to be provided between said dispersion plane andlight emitting layer. To prevent reflection loss between the lightemitting layer and the second intermediate layer in contact with thelight emitting layer, there is preferred to be no difference ofrefractive index on the contact surface.

In FIG. 15(b), the second intermediate layer (32), equipped with asurface where a group of micro lens are installed, is provided on thesurface opposite to the light emitting layer in order to bend thedirection of the light emitted from the light emitting layer (31′)upward. In this case, a distance of 10 times or more of the lightwavelength is preferred to be provided between the micro lens plane andthe light emitting layer. To prevent reflection loss between the lightemitting layer and the second intermediate layer in contact with thelight emitting layer, there is preferred to be no difference inrefractive index on the contact surface.

FIG. 15(c) shows the case where the second intermediate layer (33),provided with an internal scattering body, such as metallic fineparticles and others, is provided on the surface opposite to the lightemitting layer in order to bend the direction of the light emitted fromthe light emitting layer (31″) upward. This is intended to widen theradiation angle by scattering. There is no restriction as to thethickness. To prevent reflection loss with the second intermediate layerin contact with the light emitting layer, there is preferred to be nodifference in refractive index on the contact surface.

FIGS. 15(d), 15(e) and 15(f) correspond to FIGS. 15(a), 15(b) and 15(c),respectively. They show the configuration where simple secondintermediate layers (34,34′ and 34″) are provided among each lightemitting layer (31′″, 31″″, and 31′″″), respectively. The secondintermediate layer (30′) is provided with a surface diffusion plane, thesecond intermediate layer (32′) is provided with a microlens groupsurface, and the second intermediate layer (33′) is provided with aninternal light scattering body. There is preferred to be no differencein refractive index between the light emitting layer and the secondintermediate layer to prevent reflection on the boundary. At the sametime, absence of any difference in refractive index between the toplight discharge plane of the device and the external air is essential toimprove the discharge efficiency of the entire device. Thus, thereflection loss can be reduced by minimizing the refractive index of thefunctional second intermediate layer (30′, 32′ and 33′) provided on thetop layer and by introducing the simple type second intermediate layerwhich reduces the difference in refractive index with the light emittinglayer. It is preferred to provide a layer having a refractive indexintermediate between the two or a layer with a refractive indexdistribution which ensures gradual reduction of refractive index.

When such a light emitting layer is designed in a multiple fine pixelarrangement, as in the case of an image display device, the partitionincluding the reflection surface with an oblique plane or curve, whichensures that light generated in the direction horizontal to the lightdischarge plane in the light emitting layer is bent in the verticaldirection, can be used as the partition layer separating betweenadjacent light emitting layer pixels. This partition ensures furtherimprovement of the discharge efficiency.

Use of the organic electroluminescence device according to the presentinvention provides a higher light discharge efficiency than theconventional organic electroluminescence device. At the same time, itprovides characteristics of the optimum angle of field.

Furthermore, it makes it possible to obtain orientation conditions forthe optimum light emitting molecules of the entire device. It also makesit possible to design an orientation means in conformity to the lightemitting wavelength to be used, the direction, or the intermediatelayer. It is possible to compensate for loss on the boundary with alayer other than the device internal light emitting layer, and to adjustchanges in chromaticity. The obtained light emission produces polarizedlight in response to another light emitting material which providessecondary emission of light upon receipt of light from the lightemitting material, in addition to one light emitting material; hence,polarized light corresponding to the full color can be emitted. Thesecharacteristics provide high functions as an image display device,including a 3-D color display, based on a high contrast display withoutthe need of polarizing plate, and the state of polarization. At the sametime, they provides a flat type optical information processor for a newlight exchanger and an optical arithmetic unit.

The present invention provides an organic electroluminescence devicecharacterized by an excellent discharge efficiency, and photoelectrondevice using said electroluminescence device.

1. An organic electroluminescence device, comprising: a substrate; anelectrode formed on the substrate; a light emitting layer formed on theelectrode, the light emitting layer enabling injection of positive andnegative electrical charges therein; and an opposing electrode formedwith respect to the light emitting layer so that the light emittinglayer is arranged between the transparent electrode and the opposingelectrode; wherein the light emitting layer contains a light emittingsubstance for emitting light anisotropically, the light emittingsubstance having transition dipole moments attributable to a molecularskeleton thereof, and the transition dipole moments being orientedwithin an angular range from 0 degree to 70 degrees with respect to adirection normal to a side surface of the light emitting layer.
 2. Anelectroluminescence device according to claim 1, wherein the opposingelectrode is a transparent electrode.
 3. An electroluminescence deviceaccording to claim 1, wherein light emitted by the light emitting layeris polarized light.
 4. An electroluminescence device according to claim1, wherein light emitted by the light emitting layer has a maximumintensity within an angular range from 0 degree to 60 degrees withrespect to the direction normal to the substrate side surface of thelight emitting layer.
 5. An electroluminescence device according toclaim 1, wherein the light emitting layer further contains a fluorescentsubstance emitting secondary light upon receipt of light from the lightemitting substance.
 6. An electroluminescence device according to claim1, wherein an intensity of light emitted by the light emitting layer atan angle of at least 40 degrees with respect to the direction normal toa surface of the light emitting layer on the opposite side to thesubstrate is one half of an intensity of light emitted by the lightemitting layer in the direction normal to the surface of the lightemitting layer on the opposite side to the substrate.
 7. Anelectroluminescence device according to claim 1, wherein the lightemitting layer further contains an organic compound of ionicity.
 8. Anelectroluminescence device according to claim 1, wherein the lightemitting substance comprises an organic compound having the


9. A photoelectron device using an electroluminescence device, whereinthe electroluminescence device comprises: a substrate; an electrodeformed on the substrate; a light emitting layer formed on the electrode,the light emitting layer enabling injection of positive and negativeelectrical charges therein; and an opposing electrode formed withrespect to the light emitting layer so that the light emitting layer isarranged between the transparent electrode and the opposing electrode;wherein the light emitting layer contains a light emitting substance foremitting light anisotropically, the light emitting substance havingtransition dipole moments attributable to a molecular skeleton thereof,and the transition dipole moments being oriented within an angular rangefrom 0 degree to 70 degrees with respect to a direction normal to a sidesurface of the light emitting layer.
 10. A photoelectron device using anelectroluminescence device according to claim 9, wherein the opposingelectrode is a transparent electrode.